Compound automotive rearview mirror

ABSTRACT

A composite mirror adapted for use as an outside rearview mirror of a motor vehicle includes a main or primary viewing mirror and an auxiliary blindzone viewing mirror juxtaposed to expose the vehicle blindzone to the vehicle operator. The main viewing mirror is generally of unit magnification. The auxiliary mirror is generally composed of a convex surface that can be either attached atop the surface of the main viewing mirror or placed within a cut-out region of the main viewing mirror. The auxiliary mirror can be partially recessed below the surface of the main viewing mirror and can have a skirt for minimizing undesirable reflections in the main viewing mirror.

This application is a divisional of copending application Ser. No.10/784,668, filed on Feb. 23, 2004, which claims the benefit of U.S.provisional application Ser. No. 60/449,370, filed Feb. 21, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to mirrors having multiplesurfaces of differing magnification and, particularly, to theapplication of such mirrors as external side rearview automotiveoperator aides.

2. Background Art

Originally, motor vehicles, particularly passenger cars, did not havemirrors to assist the driver. Early in this century however, both insideand outside mirrors were added to automotive vehicles to providerearward and limited lateral visibility. As the number of vehicles anddriving speeds increased, rearward visibility became ever moreimportant.

Today, all passenger cars have a mirror centrally located inside thevehicle. This mirror is the primary mirror. It provides a wide viewingangle, giving an excellent view to the adjacent lanes at a distance oftwo or more car lengths to the rear. However, it is deficient in that itis unable to view the adjacent lanes at distances of less than one totwo car lengths to the rear. In an effort to eliminate this deficiencyand to provide rearward visibility when the rear window is blocked,outside mirrors were added to vehicles.

Presently, passenger cars are required by law to have a unitmagnification outside rearview mirror on the driver's side. A unitmagnification mirror is a plane mirror which produces the same sizeimage on the retina as that which would be produced if the object wereviewed directly from the same distance. Furthermore, as provided inFederal Motor Vehicle Safety Standard 111 (FMVSS 111), “The mirror shallprovide the driver a field of view of a level road surface extending tothe horizon from a line perpendicular to a longitudinal plane tangent tothe driver's side of the vehicle at the widest point, extending 8 feetout from the tangent plane 35 feet behind the driver's eyes, with theseat in the rear most position.” FMVSS 111 thus effectively determinesthe size of the mirror, which a manufacturer must provide. The size willvary among different manufacturer's vehicles because of the placement ofthe mirror on the vehicle with regard to the driver's seat location.

Unfortunately, outside mirrors meeting FMVSS 111 still do not provideadequate adjacent lane visibility to view cars that are in the range ofone car length to the rear. That is, a blindzone exists where a vehicleis not visible in either the inside mirror or the outside mirror. Even aglance over the shoulder may not be adequate to observe a vehicle in theblindzone. For many vehicles, the door pillar between the front and reardoors obscures the view to the blindzone. Furthermore, this obstructionis not obvious to most drivers, and they may assume that the “over theshoulder glance” has allowed them to see the blindzone when in realityit has not.

Rearward vision in automobiles is mathematically described in a paperpublished by the Society of Automotive Engineers (SAE) in 1995. Thatpaper is designated as SAE Technical Paper 950601. It is entitled, TheGeometry of Automotive Rearview Mirrors-Why Blindzones Exist andStrategies to Overcome Them, by George Platzer, the inventor of thepresent invention. That paper is hereby incorporated by reference.

A common method of overcoming the blindzone is to add a sphericallyconvex blindzone-viewing mirror to the required plane main mirror.Spherically convex mirrors provide a wide field of view, but at thepenalty of a reduced image size. However, this may be acceptable if themirror is only used to indicate the presence of a vehicle in theblindzone and it is not used to judge the distance or approach speed ofvehicles to the rear. Simply placing a round segment of a convex mirroron the main mirror surface, as is commonly done with stick-on convexmirrors, does not solve the problem. Doing so can provide a view to therear which includes the blindzone, but it will also show much of theside of the car, the sky and the road surface, which are distracting andextraneous to the safe operation of the vehicle. What is required is aconvex blindzone-viewing mirror that shows the driver primarily only theblindzone. In this way, if the driver sees a vehicle in theblindzone-viewing mirror, he knows it is unsafe to move into theadjacent lane. All extraneous and distracting information should beremoved from the blindzone-viewing mirror. Furthermore, by eliminatingthe irrelevant portions of the bull's-eye mirror, the remaining portioncan have a larger radius of curvature, thereby increasing the image sizefor the given amount of area that is to be allocated to the convexmirror.

Other problems with add-on mirrors are that they:

-   -   may interfere with the requirements of FMVSS 111;    -   may substantially decrease the plane main mirror viewing angle;    -   interfere with cleaning, especially when there is ice on it; and    -   appear as an unsightly excrescence on the main mirror. A        blindzone-viewing mirror that is provided by a car manufacturer        must not appear to be an afterthought, but rather an integral        part of the mirror.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a unit magnificationmain mirror, which meets the requirements of FMVSS 111 andsimultaneously provides a blindzone-viewing mirror having amagnification of less than unity that, in application, is able to showan automobile driver's side blindzone.

Another object of the invention is to provide a less than unitmagnification mirror that meets the requirements of FMVSS 111 on thepassenger's side and simultaneously provides a blindzone-viewing mirrorhaving a magnification of less than unity that is able to show thedriver the blindzone on the passenger's side.

Yet another object of the invention is to provide a mirror having acombination of two surfaces of different magnification that is notobjectionable in appearance.

Still another object of the invention is to provide a mirror having acombination of two surfaces of different magnification that isinexpensive and easy to manufacture.

In an embodiment of the invention, an auxiliary blindzone viewing mirrorhaving a less than unit magnification can be adhesively attached to amain viewing mirror. The auxiliary blindzone viewing mirror can becomprised of a discrete mirror body can be optimized in size andorientation to provide primarily only a view of the blindzone whileleaving the region surrounding it available to meet the requirements ofFMVSS 111. Moreover, the discrete mirror body can be comprised of arecessed ledge formed in a base of the auxiliary mirror for retainingadhesive while maintaining flush contact with the main viewing mirror.The auxiliary blindzone viewing mirror can be located in the upper andouter region of the main viewing mirror.

In another embodiment of the invention, an auxiliary blindzone viewingmirror can be inserted into a cut-out region of a main viewing mirror.The auxiliary blindzone viewing mirror can comprise a convex reflectivesurface optimized in size and orientation to provide primarily only aview of the blindzone while leaving the region surrounding it availableto meet the requirements of FMVSS 111. The auxiliary blindzone viewingmirror having a rim about its perimeter for resting against a surface ofthe main viewing mirror. The rim can be canted to obscure the reflectionof the auxiliary blindzone viewing mirror in the main viewing mirror.

In still another embodiment of the present invention, an automotiveoutside rearview mirror comprising a main viewing mirror having agenerally planar reflective surface, an auxiliary blindzone viewingmirror having a generally convex reflective surface, and a case forretaining both mirrors is provided. The auxiliary blindzone viewingmirror is shaped and positioned for viewing primarily only a driver'sblindzone. The automotive outside rearview mirror further comprises alip along the border between the main viewing mirror and the auxiliaryblondzone viewing mirror. The lip comprises a canted surface forobscuring the reflection of the auxiliary blindzone viewing mirror inthe main viewing mirror. Moreover, the lip can be integrally formedwithin the auxiliary blindzone viewing mirror, or rather, the lip can beintegrally formed within a wall formed in the case.

These and other aspects, objects, features and advantages of the presentinvention will be more clearly understood and appreciated from a reviewof the following detailed description of the preferred embodiments andappended claims, and by reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may best be understood withreference to the following description, taken in connection with theaccompanying drawings which:

FIG. 1 is a plan view of an automobile on a three-lane highway depictingthe field of view of the automobile's outside mirrors and theblindzones;

FIG. 2 is a diagram showing the requirements of FMVSS 111 for thehorizontal field of view of the driver's outside mirror;

FIG. 3 is a diagram showing the requirements of FMVSS 111 for thevertical field of view of the driver's outside mirror;

FIG. 4 is an image of the road as seen in the driver's outside mirrorshowing the effect of the requirements of FMVSS 111 on the horizontalwidth and the vertical height of the mirror;

FIG. 5 is a perspective drawing showing how a less than unitmagnification mirror can be placed on the driver's outside mirror toavoid conflicting with the requirements of FMVSS 111 and yet provide awide angle mirror to observe the blindzone;

FIG. 6 is a front view of the mirror of FIG. 5;

FIG. 7 is side sectional view of the mirror of FIG. 6 in the plane alongline 7-7 in the direction of the arrows showing the proper location ofthe center of the sphere on which the surface of the blindzone mirrorlies, so as to produce vertical centering of the image of a vehicle thatis in the blindzone;

FIG. 8 is a top sectional view of the mirror of FIG. 6 in the planealong line 8-8 looking in the direction of the arrows showing the properlocation of the center of the sphere on which the surface of theblindzone mirror lies, so as to produce horizontal centering of theimage of a vehicle that is in the blindzone;

FIG. 9 is a plan view of a two lane highway showing a vehicle in theright lane equipped with the mirror of FIG. 5 and four positions of anovertaking vehicle in the left lane;

FIG. 10 a shows the image of an overtaking vehicle in FIG. 9, in amirror like that of FIG. 5;

FIG. 10 b is like FIG. 10 a except that the overtaking vehicle isfarther to the rear;

FIG. 10 c is like FIG. 10 b except that the overtaking vehicle isfarther to the rear;

FIG. 10 d is like FIG. 10 c except that the overtaking vehicle isfarther to the rear;

FIG. 11 is a perspective view of an auxiliary blindzone viewing mirrorhaving straight edges depicting how the reflection of the auxiliaryblindzone viewing mirror can be seen in the main viewing mirrorobscuring the driver's perception;

FIG. 12 is a plan view of an auxiliary blindzone viewing mirroraccording to an embodiment of the present invention;

FIG. 13 is side view of the auxiliary blindzone viewing mirror shown inFIG. 12;

FIG. 14 is a sectional view of the auxiliary blindzone viewing mirrorshown in FIG. 12 taken along the line 14-14;

FIG. 15 is a plan view of a main viewing mirror according to anembodiment of the present invention;

FIG. 16 is a plan view of an automotive outside rearview mirror assemblyhaving an auxiliary blindzone viewing mirror according to an embodimentof the present invention;

FIG. 17 is an enlarged plan view of the auxiliary blindzone viewingmirror shown in the upper and outer quadrant of the automotive outsiderearview mirror assembly in FIG. 16;

FIG. 18 is an elevational view of the auxiliary blindzone viewing mirrorshown in FIG. 17;

FIG. 19 is a sectional view of the auxiliary blindzone viewing mirrorshown in FIG. 17 taken along line 19-19;

FIG. 20 is a plan view of an automotive outside rearview mirror assemblyaccording to another embodiment of the present invention;

FIG. 21 is a sectional view of the mirror assembly in FIG. 20 takenalong line 21-21;

FIG. 22 is a sectional view of the mirror assembly in FIG. 20 takenalong line 22-22;

FIG. 23 is a plan view of an automotive outside rearview mirror assemblyaccording to another embodiment of the present invention;

FIG. 24 is a sectional view of the mirror assembly in FIG. 23 takenalong line 24-24;

FIG. 25 is a sectional view of the mirror assembly in FIG. 23 takenalong line 25-25;

FIG. 26 is an enlarged plan view of a fully recessed auxiliary blindzoneviewing mirror similar to the auxiliary mirror shown in the upper andouter quadrant of the automotive outside rearview mirror assembly inFIG. 16;

FIG. 27 is an elevational view of the auxiliary blindzone viewing mirrorshown in FIG. 26;

FIG. 28 is a sectional view of the auxiliary blindzone viewing mirrorshown in FIG. 26 taken along line 28-28.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As required, detailed embodiments of the present invention are disclosedherein. However, it is to be understood that the disclosed embodimentsare merely exemplary of an invention that may be embodied in various andalternative forms. Therefore, specific functional details disclosedherein are not to be interpreted as limiting, but merely as arepresentative basis for the claims and/or as a representative basis forteaching one skilled in the art to variously employ the presentinvention.

Referring now in greater detail to the drawings, FIG. 1 shows amid-sized passenger car 10 in the middle lane of a three-lane highwaywith 12-foot wide lanes. The vehicle 10 is equipped with a driver's sideoutside mirror 12. The driver's eyes are shown centered at point 14,from which the driver has a field of view to the rear in the horizontalplane encompassing the acute angle formed by lines 16 and 18. Line 20defines the rearward limit of the driver's peripheral vision whenlooking at mirror 12. Thus, the area bounded by lines 18 and 20 is ablindzone, shown crosshatched, which cannot be observed in either thedriver's direct forward vision or indirectly in the mirror.

SAE Technical Paper 950601 describes the horizontal field of view of aplane mirror in a mathematical equation as a function of the mirror'sdimensions and the position of the eyes relative to the mirror.Typically, the angle θ subtended by lines 16 and 18 is in the order of15° to 20°. Angle θ is given by Eq. 1, and it is, $\begin{matrix}{{\theta = {2\quad{\tan^{- 1}\left\lbrack \frac{{w\quad\cos\quad\lambda} + D}{2\sqrt{s_{L}^{2} + s_{T}^{2}}} \right\rbrack}}},} & {{Eq}.\quad 1}\end{matrix}$where:

-   -   w=mirror width;    -   D=interpupillary distance;    -   S_(L)=the longitudinal distance along the axis of the vehicle        from the driver's eyes to the center of the mirror;    -   S_(T)=the transverse distance perpendicular to the longitudinal        axis from the driver's eyes to the center of the mirror; and    -   λ=½ tan⁻¹ (S_(T)/S_(L))

As described in SAE Technical Paper 950601, the peripheral vision line20 cannot be precisely located. It depends on the location of thedrivers' eyes relative to the mirror 12 and several other factors. Forexample, Burg (Journal of Applied Psychology/Vol. 5/No. 12/1968) hasshown that the angular extent of peripheral vision is a function of age.At age 20 it extends 88° from straight-ahead to the side. At 70 years,this angle has dropped to 75°. Angle φ in FIG. 1 is the angle of theperipheral vision line 20 relative to line 22, which is perpendicular tothe longitudinal axis of vehicle 10. Typically this angle will be in therange of 40 degrees.

FIG. 2 shows the requirement imposed on the width of mirror 12 by FMVSS111. As previously stated, the mirror 12 must be able to show a point,as 24, which is 244 cm (8 feet) out from a plane 26 tangent to the sideof the vehicle and 1067 cm (35 feet) behind the driver's eyes with theseat in the rear most position. Point 28 is 1067 cm behind the driver'seyes and in plane 26. Points 24 and 28 are on the road surface. Angle θin FIG. 2 is obviously, $\begin{matrix}{\theta = {{\tan^{- 1}\left( \frac{244}{S_{L} + 1067} \right)}.}} & {{Eq}.\quad 2}\end{matrix}$

Angle θ has a value of about 11.5° for almost any passenger car, and thevariation in θ produced by variations in S_(L) is a second order effect.Hence, the width of the mirror required by FMVSS 111 can be calculatedby solving Equation 1 for w. Then, $\begin{matrix}{w = {\frac{{2\sqrt{s_{L}^{2} + s_{T}^{2}}\left( {\tan\quad\frac{\theta}{2}} \right)} - D}{\cos\quad\lambda}.}} & {{Eq}.\quad 3}\end{matrix}$

Angle θ in this case is equal to 11.5°. Using values of S_(L)=45.7 cm,S_(T)=70 cm, and D=6.4 cm, w is found to be 9.4 cm. This value can varysignificantly among vehicles, since in Eq. 3, S_(L) and S_(T) variationsno longer produce only second order effects as in Eq. 2. In practice,vehicle manufactures will specify mirror widths in excess of the FMVSS111 requirements to further reduce the blindzone size.

FIG. 3 shows the requirements imposed on the vertical dimension ofmirror 12 by FMVSS 111. In the vertical plane, vision is monocular sincethe eyes are not separated as they are in the horizontal plane. SAETechnical Paper 950601 shows that for monocular vision, theinterpupillary distance D drops out of Equation 1, so that it becomes,$\begin{matrix}{\theta = {2\quad{{\tan^{- 1}\left\lbrack \frac{w\quad\cos\quad\lambda}{2\sqrt{s_{L}^{2} + s_{T}^{2}}} \right\rbrack}.}}} & {{Eq}.\quad 4}\end{matrix}$Then, $\begin{matrix}{w\quad = \quad{\frac{2\quad\sqrt{\quad{S_{L}^{2}\quad + \quad S_{T}^{2}}}\quad\tan\quad\frac{\theta}{2}}{\cos\quad\lambda}.}} & {{Eq}\quad.\quad 5}\end{matrix}$

In FIG. 3, h is the height in cm of mirror 12 above the ground, and itcan vary significantly from a sports car to a sedan to a van. Angleθ_(V) is the angle that determines what the vertical dimension, w_(v),of mirror 12 must be, in conjunction with the distance of the eye fromthe mirror. Angle θ_(V) replaces angle θ in Equation 5 when calculatingthe vertical dimension of the mirror. Applying Equation 5 to therequired vertical dimension of the mirror, w_(v), $\begin{matrix}{{w_{V}\quad = \quad\frac{2\quad\sqrt{\quad{S_{L}^{2}\quad + \quad S_{V}^{2}}}\quad\tan\quad\frac{\theta_{V}}{2}}{\cos\quad\lambda_{V}}},} & {{Eq}\quad.\quad 6}\end{matrix}$where: S_(v)=vertical distance in the vertical plane from the eye to themirror;

λ_(V)=½ tan⁻¹(S_(V)/S_(L)); and$\theta_{V} = {{\tan^{- 1}\left( \frac{h}{S_{V} + 1067} \right)}.}$Substituting measured values of h, S_(L), and S_(V) from one mid-sizepassenger car gave a value for w_(v) of 6.4 cm.

The FMVSS 111 requirement for the vertical dimension of the mirror isonly a minimum, and it does not provide a satisfactory mirror. Driversusually set their mirrors so that if the car is on a straight and levelroad, the horizon will be in about the center of the mirror. This meansthat if point 24 is to be visible with the horizon centered, the mirrorshould be about 12.7 cm high. Most passenger car mirrors are not thislarge vertically, and are closer to 10.2 cm to 11.4 cm. However, therequirements of the standard are met.

FIG. 4 shows mirror 12 adjusted so that the horizon 30 lies at itscenter. Point 24 is shown in the lower left-hand corner. Also shown ispoint 28 in the right-hand corner. Line 32 represents the dashed yellowlane marker between the two left lanes. Line 34 represents the left edgeof the left lane. Lines 32 and 34 converge at infinity on the horizon.The mirror has been adjusted so that point 28 is just visible, i.e.rotating the mirror farther outward would make point 28 disappear fromview.

As previously mentioned, a mirror constructed to just meet therequirement in its horizontal field of view would have an excessivelylarge blindzone. This could be remedied by providing an auxiliaryblindzone-viewing mirror of less than unit magnification with a widefield of view, located such that it does not interfere with line 34.Such an auxiliary mirror 36 is shown in FIG. 5 attached to a plane mainviewing mirror 40. Mirror 36 is a spherically convex mirror havingdimensions and an orientation such that its field of view encompassesthe region in FIG. 1 between lines 18 and 38. Mirror 36 can be madesmall enough so that is does not excessively encroach on the plane areaof the main viewing mirror 40 above line 34. For example, if mirror 40is 10 cm wide, mirror 36 could easily be 4.4×4.4 cm square. Using 4.4 cmas the horizontal dimension for mirror 36, the radius of curvaturerequired to encompass the blindzone can be calculated from anotherequation in SAE Technical Paper 950601. There it is shown that the fieldof view of a convex mirror is, $\begin{matrix}{\theta = {{2\left\lbrack {{2\tan^{- 1}\frac{w}{\quad{2\quad r}}} + {\tan^{- 1}\frac{{w\quad\cos\quad\lambda}\quad + \quad D}{\quad{2\quad\sqrt{\quad{s_{\quad L}^{\quad 2}\quad + \quad s_{\quad T}^{\quad 2}}}}}}} \right\rbrack}.}} & {{Eq}.\quad 7}\end{matrix}$All of the variables in Equation 7 are the same as Equation 1 except forr, which is the radius of curvature of the convex mirror. Angle θ inEquation 7 is to be taken as the angle between lines 18 and 38 inFIG. 1. Line 38 is seen to extend from mirror 12 and intersect theperipheral vision line 20 in the center of the adjacent lane. The anglebetween lines 18 and 38 is about 25°. Using w=4.5 cm, S_(L)=45.7 cm,S_(T)=26.5 cm and D=6.4 cm, r calculates out to be 27.8 cm. Selection of25° as the blindzone width is partially subjective. It involves thechoice of the peripheral vision angle, the positioning of the mirror andan estimate of how much of the geometrically defined blindzone must beincluded to assure that a driver is able to see a vehicle in theblindzone. In general a radius of curvature in the range of 20 cm to 35cm will be satisfactory depending upon the vehicle.

A key factor in the shaping and positioning of the blindzone-viewingmirror is the required location of the center of the sphere from whichthe segment is taken. A vehicle in the blindzone should appear centeredin the auxiliary blindzone-viewing mirror. FIGS. 6, 7 and 8 comprise ageometric orthographic projection showing the proper orientation of aspherically convex mirror segment 36 relative to a plane mirror 40. Aradius 42 and an arc 44 of the sphere from which segment 36 is taken,must pass through the center 46 of the face of segment 36. The locationof the center of the sphere must be specified so that centering of theimage of a vehicle in the blindzone will occur.

As previously stated, most drivers adjust their mirrors so that if theywere on a straight and level road, the horizon would be approximatelycentered in the mirror. Vertical centering of an image in theblindzone-viewing mirror 36 then requires that the image of the horizonpass through center 46 of mirror 36. This simply requires that radius 42lie in a plane perpendicular to plane mirror 40, and that the plane alsopass through center point 46, as shown in FIG. 7.

Horizontal centering of the view of the blindzone in mirror 36 requiresthat radius 42 be located such that it passes through center 46 ofmirror 36 and also falls along line 48 in FIG. 1 which bisects the acuteangle formed by lines 18 and 38. The actual position of radius line 42in FIG. 8 relative to the vehicle is dependent upon how the driver haspositioned the mirror relative to the vehicle. However, the position ofline 42 relative to line 50 in FIG. 8 is constant. If the driver isinstructed to position the plane mirror so that the side of the car isjust visible, the position of line 42 is then effectively constantrelative to the side of the vehicle, and the blindzone view iseffectively centered about line 48 in FIG. 1.

The field of view in the plane main viewing mirror is θ degrees wide asshown in FIG. 1. If the driver so chooses, he or she could readjust themain viewing mirror so angle θ straddles line 48. Then, the plane mirrorview would be centered on the blindzone. Many drivers actually set theirmirrors this way to view the blindzone. Since the angle of reflection isequal to the angle of incidence, rotating the field of view outward bysay 30°, would require rotating the mirror outward by 15°. Hence, tomake the plane mirror look into the center of the blindzone requiresthat it be rotated by ½ of the angle between line 48 and line 52, whereline 52 bisects angle θ. Again selecting the blindzone width as 25°, andusing a value of 15° for θ, the field of view would have to be rotated ½(25 °+15°)=20°. This would require rotating the mirror 10° to look intothe center of the blindzone with the plane mirror.

The same reasoning applies to the convex blindzone-viewing mirror. Ifradius 42 were perpendicular to the surface of plane mirror 40, thefield of view of the convex mirror would be centered about line 52 inFIG. 1. But we want the spherical mirror's field of view to be centeredabout line 48 when the plane mirror is adjusted to just see the side ofthe vehicle. Therefore in FIG. 8, line 42 should be at an angle β of 10°to line 50. The exact angle β chosen will be dependent upon the vehicleand the assumptions made for the position of line 48 in FIG. 1.

The criteria required to size, place and orient the less than unitmagnification auxiliary blindzone-viewing mirror have now beenestablished. Using these criteria will provide a mirror which conformswith FMVSS 111, centers the image of a vehicle in the blindzone in theless than unit magnification mirror, and optimizes the image size forthe space allocated to the less than unit magnification mirror. Mirror36 in FIG. 5 may be visualized as a spherically convex bulls eye mirrorwherein all extraneous portions of the bulls eye have been removed,leaving only that portion which will show a vehicle in the blindzone.When driving with a mirror so configured, a vehicle overtaking on thedriver's side will be seen in the main viewing mirror when the vehicleis to the rear of the blindzone. As the vehicle approaches, it appearsto slide outwardly off of main viewing mirror 40 and ontoblindzone-viewing mirror 36. FIG. 9 shows an overtaking vehicle atvarious distances behind vehicle 10 of FIG. 1. FIGS. 10 a, 10 b, 10 cand 10 d show the position of the image of the overtaking vehicle onmirror 12 in FIG. 9. FIG. 10 d shows the image of the overtaking vehicleat a position 11 d in FIG. 9 about 12 car lengths to the rear of vehicle10. Note that a small portion of the left rear fender of vehicle 10 isseen in the lower right-hand corner of the plane main mirror. FIG. 10 cshows the image of the vehicle at a position 11 c about 3.5 car lengthsto the rear. FIG. 10 b shows the image of the vehicle at position 11 babout 1.25 car length back, and it is seen mostly in the plane mainviewing portion of the mirror, but partially in the auxiliaryblindzone-viewing portion. FIG. 10 a shows the image of the overtakingvehicle in position 11 a, which is entirely in the blindzone, and it isseen that the image is entirely in the blindzone-viewing mirror. Thus,the image of the approaching vehicle moves from inside to outside acrossthe mirror, and this is one reason why the auxiliary mirror is placed inthe upper and outer quadrant of the rearview mirror. Placing it on theinner quadrant would disturb the apparent flow of the image of theovertaking vehicle as it moves across the main mirror from inside tooutside.

Next, various ways of implementing the combination of the main viewingmirror and the blindzone-viewing mirror will be shown. One simple way isto adhere a glass or plastic segment of a spherically convex mirror tothe plane mirror, as shown in FIG. 5. However, the spherically convexstick-on mirror shown in FIG. 5 is not without some crude andundesirable features. For example, one such feature is that the sides ofthe stick-on mirror are straight. As such, the sides are reflected inthe plane mirror, which the stick-on mirror is mounted upon, appearingto double the height of the stick-on mirror. FIG. 11 shows a planemirror 54 with a stick-on mirror 56 having straight sides. A reflection58 of the top edge of stick-on mirror 56 in plane mirror 54 is depictedby a dashed reference line. The reflection 58 is plane mirror 54 can beboth distracting and unattractive.

FIGS. 12 and 13 show a stick-on auxiliary blindzone viewing mirror 60,according to an embodiment of the presentation, having a skirt 62 aroundits perimeter. The skirt 62 can have canted or flared sides to hide thereflection of stick-on mirror 60 in a plane mirror. Preferably, theskirt extends outward along its base by an amount of about one half ofthe height of mirror 60 above its base 64 as indicated by dashed lines66 and 68. Surface 70 may be flat or curved. Also, if mirror 60 is asingle piece injection molded plastic with a reflective coating appliedto it, surface 70 preferably has a matte finish to avoid reflectionsfrom that surface.

Another advantage of the skirt 62 is that it helps to blend theauxiliary mirror 60 into a planar main viewing mirror making it appear amore integral part of the main mirror. This is especially true if thebase 64 can be made flush with the main mirror. However, it is importantto note that adhering the stick-on auxiliary mirror 60 to the mainmirror with a thin film of an adhesive having a high modulus ofelasticity may be undesirable. For instance, the difference in thermalexpansion between the auxiliary mirror 60 and the typical glass mainmirror, along with the rigidity of the bond, may cause warping anddistortion of an image in the main mirror. The image distortion isgenerally observable when the ambient temperature is 20° F. or more awayfrom the bonding temperature.

To achieve a close fit between the auxiliary mirror 60 and a main mirrorsurface 71 and to avoid distortion, a shallow ledge 72 can be providedin the base 64 of the auxiliary mirror 60, as shown in FIG. 14. Ledge 72can be located inboard of the bottom perimeter of auxiliary mirror 60 byabout 2 or 3 millimeters. Further, edge 72 can be about 1 millimeterdeep. A bead of adhesive 73 such as Dymax 4-20533, which has a lowmodulus of elasticity and sets to a rubbery consistency, can be appliedalong the ledge 72. Auxiliary mirror 60 can now be pressed flat againstthe main mirror surface 71. Accordingly, the adhesive 73 fills ledge 72while the excess adhesive flows into a cavity 74. Cavity 74 can retainthe excess adhesive while reducing part weight and the materialnecessary to form auxiliary mirror 60. The adhesive 73 in the ledge 72can now hold auxiliary mirror 60 firmly in place while absorbing anydifferences in thermal expansion. It is fully contemplated that anytypical adhesive with a low modulus of elasticity can be used. Moreover,it may be desirable to use an adhesive capable of being cured withultraviolet light.

Alternately, a double sided adhesive pad 75 may be used to affixauxiliary mirror 60 to the main mirror surface 71. The ledge 72 can beutilized to retain the pad 75. Thus, the pad 75 can be die cut to fitthe ledge 72. Moreover, the depth of the ledge 72 and the thickness ofthe pad 75 can be sized to produce the minimum protrusion of the pad 75below the base 64 of auxiliary mirror 60 that will still provideadequate adhesion to the main mirror surface 71. The width of ledge 72can be extended inward when using the double sided adhesive pad 75 toincrease the adhered area. Furthermore, the lightening volume defined bycavity 74 may be eliminated. Accordingly, the adhesive pad 75 may be adesirable alternative for aftermarket applications.

Yet another advantage of the skirt 62 on auxiliary mirror 60 is that thecanted or flared surface 70 can act as a deflector of impact loads, suchas that produced by an ice scraper. The skirt 62 tends to deflect thescraper away from the auxiliary mirror 60, thereby minimizing thelikelihood of dislodging the auxiliary mirror 60 from the main mirrorsurface 71.

Referring back to FIG. 8, the convex surface of a blindzone-viewingauxiliary mirror attached to a planar main mirror will vary in heightabove the surface of the planar main mirror. The right edge of stick-onmirror 36 is shown to be higher above the surface of main mirror 40 thanthe left edge. A blindzone viewing mirror having a viewing angle of 25°and a base having dimensions of 50 mm×50 mm, for example, may have aheight of about 6 mm at the right edge. This height rolls off to about 1mm at the left edge. In some instances, it may be desirable to improvethe appearance of the combined mirrors by recessing the auxiliary mirrorpartially below the surface of the main mirror. A semi-recessedauxiliary blindzone mirror can be esthetically more pleasing than onethat is fully recessed.

With reference now to FIGS. 15-19, an automotive outside rearview mirrorassembly 77 according to an embodiment of the present invention isshown. The glass in a particular area of a planar main mirror 76 inwhich a blindzone viewing auxiliary mirror shall be mounted can be cutout. For example, the glass in the upper and outer quadrant of mainmirror 76 can be removed, as illustrated by FIG. 15. FIG. 16 shows anauxiliary blindzone mirror 78 inserted into the cut-out region of mainmirror 76. The auxiliary mirror 78 is shown in greater detail in FIGS.17, 18, and 19. The auxiliary mirror 78 can be a convex mirror designedto be semi-recessed below the plane of the surface 84 of main mirror 76.For example, approximately half of convex surface 80 lies below surface84, while the remainder of convex surface 80 lies above surface 84. Ofcourse, it is fully contemplated that the auxiliary mirror 78 can befully recessed such that the convex surface 80 lies on or below theplane of surface 84 of main mirror 76 (as shown in FIGS. 26-28.Auxiliary mirror 78 is preferably injection molded. However, othermethods known in the art for manufacturing auxiliary mirror 78 can beemployed without departing from the scope of the present invention. Areflective coating 81 is then applied to surface 80. A rim 82 can beformed around the convex surface 80 to engage the surface 84 of mainmirror 76. An adhesive may be used to attach rim 82 to main mirror 76.FIG. 19 is a sectional view taken along line 19-19 of FIG. 17 showingmore clearly the contour of the convex mirror surface 80 above and belowthe plane of the surface 84 of the main mirror 76. Again, a skirt 83(best shown in FIGS. 18 and 19), can be formed on the rim 82 to avoidundesirable reflections of the auxiliary mirror 78 in the main mirror76. Moreover, a recessed ledge 85 can also be used for adheringauxiliary mirror 78 to main mirror 76.

Rim 82 is depicted in FIG. 17 as having the same width around theperimeter of convex surface 80. In practice, the width of rim 82 canvary at different segments around the perimeter of auxiliary mirror 78.The width of rim 82 can be especially dependent on the position ofauxiliary mirror 78 upon the surface 84 of the main mirror 76. The rim82, for example, may be very narrow at the outer edge, as shown in FIG.16.

Generally, outside rearview glass main mirrors are held in a thininjection molded plastic case. The case is used to cover and protect theedges of the glass. The back surface of the case provides an attachmentmember for connecting the mirror to the case. The attachment member istypically coupled to a positioning mechanism used to move the plane ofthe mirror about a central pivot point for positioning the view seen bythe driver. Typically, the case will have slots which are used to engagetangs on the surface of a pivoting plate which is supported on a centralpivot point. The plate can be pivoted by electric motors or cables. Themirror assembly 77 of FIG. 16 can be held in such a case. However, adepression in the case may be required to accommodate the auxiliaryblindzone mirror 78.

Referring to FIGS. 20-22, an automotive outside rearview mirror assembly86 according to an embodiment of the present invention is illustrated.The mirror assembly 86 is generally comprised of a glass main mirror 88and a convex auxiliary blindzone viewing mirror 90 mounted in a case 92.Auxiliary mirror 90 can differ from the auxiliary mirror 78 of FIG. 16by not requiring a rim surrounding the entire perimeter of the auxiliarymirror. Rather, a lip 98 can be formed along the inboard edges ofauxiliary mirror 90 for extending out over main mirror 88. Auxiliarymirror 90 can have a spherically convex surface 93, which starts at ahigh point 94 and rolls off to a low point 96 (best shown in FIG. 21). Aback surface 100 of auxiliary mirror 90 can follow a curved surfacewhich begins at a point 102 and rolls off to a point 104. The distancebetween point 96 and 104 can be about 1 mm. The case 92 follows thecontour of back surface 100. Auxiliary mirror 90 may be held in place byan adhesive between lip 98 and main mirror 88. Moreover, an adhesivebetween back surface 100 and the case 92 may be employed to secureauxiliary mirror 90. As shown in FIG. 22, a wall 106 can be formed whichsupports the lip 98 in the general region between points 108 and 110(shown in FIG. 20). Point 108 refers to the general location just beforeconvex surface 93 drops below the first surface of main mirror 88.

FIGS. 23, 24, and 25 depict yet another embodiment of a semi-recessedauxiliary blindzone mirror, in accordance with the teachings of thepresent invention. FIG. 23 shows an automotive outside rearview mirrorassembly 112 incorporating a planar main mirror 114, a blindzone viewingauxiliary mirror 116, and a case 118. Mirror assembly 112 differs fromprevious embodiments in that a skirt 119 required to eliminate theundesirable reflections of auxiliary mirror 116 in main mirror 114 canbe provided by the case 118. A wall 120 having a canted top formingskirt 119 can be molded into case 118 running entirely along the cut-outsection of the glass. The glass in this region is indicated by thehidden edge line 122. Auxiliary mirror 116 can be a spherically convexplate, which may be injection molded plastic or glass. The auxiliarymirror is preferably a first surface mirror. Further, the surface 121 ofcase 118 behind auxiliary mirror 116 can have a similar surface contouras the back surface 123 of auxiliary mirror 116. Accordingly, auxiliarymirror 116 can be adhered to the case 118 by an adhesive applied betweenthe back surface 123 of the auxiliary mirror 116 and the surface 121 ofthe case 118.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. An auxiliary blindzone viewing mirror for attachment to a mainviewing mirror having a generally planar surface, the auxiliaryblindzone viewing mirror comprising: a discrete mirror body defining asegment of a convex mirror having a reflective surface, the convexmirror having a radius of curvature and a magnification less than thatof the main viewing mirror, the discrete mirror body being shaped andpositioned for viewing primarily only a driver's blindzone encompassingthe region between the outer limit of the viewing angle of the mainviewing mirror and the rearward limit of the driver's peripheral visionwhen the driver is looking at the main viewing mirror, the discretemirror body having a generally planar base for mating engagement withthe generally planar surface of the main viewing mirror, the base havingan outer peripheral edge and a recessed ledge formed inboard of theouter peripheral edge.
 2. The blindzone viewing mirror of claim 1,wherein the discrete mirror body is formed from injection moldedplastic.
 3. The blindzone viewing mirror of claim 1, wherein a bead ofadhesive can be applied to the recessed ledge for adhesively attachingthe blindzone viewing mirror to the main viewing mirror while permittingthe base of the blindzone viewing mirror to mate flush with the planarsurface of the main viewing mirror.
 4. The blindzone viewing mirror ofclaim 3, wherein the adhesive has a generally low modulus of elasticityfor absorbing differences in thermal expansion and avoiding stress thatwould produce distortion of images.
 5. The blindzone viewing mirror ofclaim 3, further comprising an interior cavity inward of the recessedledge for retaining excess adhesive which may flow from the recessedledge.
 6. The blindzone viewing mirror of claim 1, further comprising adouble-sided adhesive pad, the adhesive pad being retained in therecessed ledge of the blindzone viewing mirror, the thickness of the padbeing sized to produce the minimum protrusion of the pad below the basesufficient to provide adequate adhesion of the blindzone viewing mirrorto the main viewing mirror.
 7. An automotive outside rearview mirrorassembly comprising: a main viewing mirror having a generally planarreflective surface; a blindzone viewing mirror having a discrete mirrorbody adhesively attached to the main viewing mirror, the discrete mirrorbody defining a segment of a convex mirror having a reflective surface,the convex mirror having a radius of curvature and a magnification lessthan that of the main viewing mirror, the discrete mirror body beingshaped and positioned for viewing primarily only a driver's blindzoneencompassing the region between the outer limit of the viewing angle ofthe main viewing mirror and the rearward limit of the driver'speripheral vision when the driver is looking at the main viewing mirror,the discrete mirror body having a generally planar base for matingengagement with the generally planar surface of the main viewing mirror,the base having an outer peripheral edge and a recessed ledge formedinboard of the outer peripheral edge; and an adhesive member disposedalong the recessed ledge between the blindzone viewing mirror and themain viewing mirror for retaining the blindzone viewing mirror to themain viewing mirror.
 8. The automotive outside rearview mirror assemblyof claim 7, wherein the blindzone viewing mirror is located in the upperand outer quadrant of the main viewing mirror.
 9. The automotive outsiderearview mirror assembly of claim 7, wherein the blindzone viewingmirror is comprised of injection molded plastic.
 10. The automotiveoutside rearview mirror assembly of claim 7, wherein the adhesive membercomprises a bead of adhesive having a generally low modulus ofelasticity.
 11. The automotive outside rearview mirror assembly of claim7, wherein the adhesive member comprises a double-sided adhesive pad,the adhesive pad being retained within the recessed ledge of theblindzone viewing mirror.
 12. The automotive outside rearview mirrorassembly of claim 11, wherein the thickness of the adhesive pad is sizedto produce the minimum protrusion of the adhesive pad below the basesufficient to provide adequate adhesion of the blindzone viewing mirrorto the main viewing mirror.